Could be any part of the ignition system. Oil in plug wells? Water on the dis PAC, from the scuttle or a leaking hbv is not uncommon for example.
As the coil PAC is a mare to get at, comparively speaking, and given likelyhood of oil in plug wells from failed cam cover gaskets and blocked breathers, a normall course of action would be to check/change the plugs. In doing so, any oil or damaged plug leads at the plug end will hopefully be obvious.
If no problems found and symptoms persist, then look at dis PAC, and possibly new leads while your there...?
Dis PAC tends to fail in pairs of cylinders, as it shares its three iron coors over 6 cylinders. So if one iron coor goes down, you can get one cylinder on each bank missing, this still gives a balanced engine and the car sounds like a scooby flat four.
Where as a misfire on , say, one cylinder, or two cylinders on the same bank, is far more noticeable as the the engine is unbalanced and can give quite bad vibration, and IME tends to be far more pronounced.